Cops are eyeing a fired construction supervisor in the murder of a Staten Island fire marshal, the lawyer for the victim’s wife said yesterday.

About a week before his death, Fire Marshal Douglas Mercereau axed the supervisor of day laborers doing renovation on the second floor of the couple’s home in Oakwood, lawyer Mario Gallucci told The Post.

“I understand the guy who was replaced was very disgruntled about it,” the lawyer said. He said the worker could had gotten into the home via a ladder left by the current crew.

The NYPD had no comment.

Gallucci is the lawyer for Janet Redmond-Mercereau, whom authorities have said is the leading suspect in the Dec. 2 killing of her husband. Douglas Mercereau was shot in the head three times at about 6:20 a.m. with his service revolver as he slept. His wife has said she was sleeping in another room and didn’t hear the shots.

Authorities said Redmond-Mercereau was angry at her husband because he made remarks about her weight.